1. Field of the Invention
The present invention concerns a rotary piston x-ray tube.
2. Description of the Prior Art
Rotary piston x-ray tubes are known, for example, from U.S. Pat. Nos. 6,426,998 and 6,339,635. An anode formed as an anode plate is disposed opposite a cathode in these known rotary piston x-ray tubes. The anode forms a base of the piston of the rotary piston x-ray tube. In the operation of the rotary piston x-ray tube, an electron beam emanating from the cathode strikes a stationary focal spot in the edge region of the anode plate. By rotation of the piston, the focal spot describes a circular focal path on the anode plate.
The heat formed by the absorption of the electrons is dissipated to a coolant via the back side of the anode plate facing away from the cathode. Given a constant radiation capacity, the heating of the anode is primarily determined by the rotational spread of the rotary piston x-ray tube as well as by the radius of the focal path. The largest possible radius of the focal path is structurally limited by the diameter of the anode plate.
Increasing the radiation capacity of the rotary piston x-ray tube leads to an increased heat entry into the anode. Since the cooling capacity of the anode is limited, for example by the maximum rotational speed, the radiation capacity of the rotary piston x-ray tube cannot be increased without further measures.
The rotational speed frequency of the rotary piston x-ray tube is limited by its moment of inertia. The massively designed anode with the anode plate contributes a significant proportion of the moment of inertia. An increase of the rotational speed for reduction of the heating of the anode is possible only to a certain degree.